Surface comes with a number of features which make it more similar to a laptop than a tablet - most notably, a built-in keyboard which could help the device appeal more to business customers.

And the fact that Microsoft is using the same Windows 8 operating system for the Surface as for laptop and desktop computers could mean that customers will find it easier to switch between different devices.

CEO Steve Ballmer was on hand at a press conference in Los Angeles to announce the tablet, calling it part of a 'whole new family of devices' the company is developing.

The 9.3mm-thick tablet, which uses the RT version of Windows, comes with a kickstand to hold it upright and keyboard that is part of the device's cover. It weighs under 1.5 pounds.

Colourful: The Surface is expected to be available for purchase some time later this year

Keyboard: The Surface's in-built keyboard is crucial to the tablet's design, making it more like using a laptop than like many other tablets

IPAD AND SURFACE SIDE-BY-SIDE

Weight: Surface 676g iPad 650g

Thickness: Surface 9.3mm iPad 9.4mm

Screen size: Surface 10.6" iPad 9.7"

USB: Surface yes iPad no

Hard drive: Surface 32GB/64GB iPad 16GB/32GB/64GB

Battery life: Surface unknown iPad around 6 hours

Price: Surface unknown iPad from $499

In a possible nod to the device's chief rival, it will apparently be 0.1mm thinner than the latest iPad.

A slightly thicker version - still less than 14mm thick and under two pounds - will work on Microsoft's upcoming Windows 8 Pro operating system.

Steven Sinofsky, the president of Microsoft's Windows division, called the device a 'tablet that's a great PC - a PC that's a great tablet.'

They will be available when Windows 8 ships later this year, according to a Microsoft statement.

No details on pricing were mentioned, except that it would be 'comparable' with current ARM tablets and Intel-powered Ultrabooks.

Microsoft has been making software for tablets since 2002, when it shipped the Windows XP Tablet PC Edition.

Many big PC makers produced tablets that ran the software, but they were never big sellers. The tablets were based on PC technology, and were heavy, with short battery lives.

Slim: The Surface is - perhaps not coincidentally - 0.1mm thinner than its chief rival, the iPad

Launching its own tablet potentially throws Microsoft into direct competition with its closest hardware partners such as Samsung and Hewlett-Packard.

Sales of tablets are expected to triple in the next two years, topping 180million a year in 2013, easily outpacing growth in traditional PCs. Apple has sold 67million iPads in two years since the device's launch.

Apple, which makes both hardware and software for greater control over the performance of the final product, has revolutionised mobile markets with its smooth, seamless phones and tablets.

Rival Google may experiment with a similar approach after buying phone maker Motorola this year.